High potential switch apparatus



Filed: April 19. 1932 IhvehtoT": PichaW-d Cr'meT",

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Patented Oct. 9, 1934 PATENT QFFHIE HEGH POTEN'EEAL SVVETCH APPARATUSRichard Criimer, Generai Eiec New York Application April 19, l

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Stegiitz, Germany, assignor to tric Company, a corporation of Serial No.606,253

In Germany April 21, 1931 4 Claims.

My invention relates to high potential switch apparatus, moreparticularly to static shielding means for preventing flashover orarcing in oil circuit breakers.

The use of insulation, as compressed paper cylinders and the like, forsurrounding the potential bearing portions of explosion chamber switchcontact structure of the high tension type is well known in the art.However as usually applied in the form of a sleeve surrounding the highpotential portions of the stationary contact structure, there may occurelectric discharges or flashovers between said contact structure andgrounded conducting portions, as the metallic switch tank or casing, orbetween the separated contact portions along a path shunting the normalcourse of the arc during the circuit interrupting operation. The abovedifficulties may, of course, be overcome by increasing the spacingbetween the metal and insulating structure in the main oil body, therebyincreasing the size of the apparatus, or by wrapping or taping theaffected parts in the manner of insulating high tension cables, thelatter method however being impractical in the case of circuit breakerssince the contact structure should be readily detachable for inspectionor replacement.

The principal object of my invention is the provision of improvedshielding means for the Q stationary contact structure of oil circuitbreakers which shall effectively prevent electric discharges between thesame and adjacent conducting structure.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is a fragmentary view, partly insection, of oil circuit breaker contact structure embodying the presentinvention, and Fig. 2 is a partial view illustrating another form of myinvention.

In Fig. 1 there is illustrated, by way of example, oil circuit breakerstructure of the so-called explosion chamber type comprising a lead-inconductor bushing l which extends in a well known manner through thecover structure of the circuit breaker, and explosion chamber contactstructure 2 supported by an adapter 3 mounted at the lower end of thelead-in bushing. The adapter 3 which is suitably connected to thelead-in conductor 1' is of metal, as is the member 4 supporting thestationary contact 4 within the explosion cham- Cal her. The movablecontact 4" carricd by the con,- ventional bridging member extendsupwardiy through the bottom of the explosion chamber to engage with thestationary contact in a well known manner. The aforesaid structure maybe of the conventional type and need not be described further for aclear understanding of the present iii-- vention.

For the purpose of preventing electric discharges at high operatingpotentials at the con- 1 tact structure, as for example between theadapter 3 and, the grounded circuit breaker tank or between thestationary contact structure .and the movable contact 4" along a pathshunting the normal course of the arc during the circuit interv ruptingoperation, there is provided a metallic cylindrical shield 5 which isccnductively connected in any suitable manner, as by a sliding contactstrip 3, with the metallic portions of the explosion chamber or adapter,the aforesaid con nection interfering in no manner with the replacementor detachment of the apparatus. The metallic shield 5, as illustrated,has a close sliding fit over the explosion chamber structure 2, theshield surrounding the metallic portions of the upper part of theexplosion chamber, the adapter and the lower part of the lead-in bushing1.

In the present instance an insulating coating 6 completely surrounds theshield 5. The outer wall of the explosion chamber structure may comprisean insulating cylinder 7, the lower part of which may support in anysuitable manner, as

by insulating rings 7, the concentric insulating cylinders 8 and 9.

High resistance of the shielding means to puncture at excessivepotentials is obtained by the above arrangement while permitting readyreplacement of the apparatus involved.

It may be advantageous in certain cases from the viewpoint of economy touse a metallic pro tecting shield insulated only in part. In Fig.

2 there is shown an arrangement wherein a metallic protecting shield 10is mounted, as in the previous instance, on the explosion chamberstructure 2, the opposite ends of the cylinder being provided withcomparatively thick walled insulating bands, each comprising a metallicband 11 and an insulating coating 12. Each band 11 is electricallyconnected as at 11' to the shield 10. Accordingly by this arrangement,the bare 105. shield 10 is provided with thick walled extensions encasedin insulating material, thereby serving to prevent discharge at theouter ends of the shield. As in the previous instance, the metallicshield projects a certain distance beyond the metallic potential bearingportions and the shield is suitably electrically connected by theconducting strip 3 to said metallic portions. It will be apparent thatthe thick-walled end portions may comprise turned-over edges of theshield itself.

An oil circuit breaker having a metallic static shield of the aforesaidcharacter may be comparatively compact in construction since a smalleroil tank may be used. Likewise the opening stroke of the breaker may beshortened. In the event of inspection or repair of the contact structurethe static shield, which is slidably mounted on the stationary contactstructure, may be readily detached, there being no permanent electricalconnections with the adapter structure to interfere.

It should be understood that my invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artWithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In an oil circuit breaker including. a lead-in conductorbushing andstationary contact structure mounted at the lower end of said bushing, ametallic static shield surrounding and having a detachable sliding fitwith respect to said contact structure, said shield and contactstructure being electrically connected by sliding electricalconnections.

2. In an oil circuit breaker including a lead-in conductor bushing andstationary contact structure mounted at the lower end of said bushing, ametallic static shield insulated at its opposite ends surrounding andhaving a detachable sliding fit with respect to said contact structure,said shield electrically connected to said contact structure.

3. In an oil circuit breaker including a lead-in conductor bushing, baremetallic structure including an adapter mounted at the lower end of saidbushing and stationary contact structure supported by said adapter, acylindrical metallic shield provided with an insulating coatingdetaohably mounted over said metallic structure, said shieldelectrically connected to said metallic structure and extending beyondthe extremities thereof.

4. In an oil circuit breaker including a lead-in conductor bushing, baremetallic contact structure mounted at the lower end of said bushing, aprotecting metallic static shield forming a cylinder. detachably mountedover and electrically connected to said contact structure and extendingbeyond the extremities thereof, and metallic bands electricallyconnected to said shield and provided with an insulating coating mountedon and disposed at the opposite ends of said cylindrical shield formingthick-Walled end portions.

RICHARD CRAMER.

